CSC 415 OPERATING SYSTEMS ALL UNITS. EXAM QUESTIONS AND ANSWERS GRADED A+ 2026

CSC 415 OPERATING SYSTEMS ALL
UNITS. EXAM QUESTIONS AND
ANSWERS GRADED A+ 2026




I/O subsystem is integrated into process manager, memory manager and file system.


Select one:
True

False - ANS False


Device drivers


Select one:
a. manage only the basic I/O hardware elements
b. manage only the newly emerging I/O devices that are unlike previous devices
c. All the other answers

d. present a uniform device- access interface to the I/O subsystem - ANS d. present a uniform
device- access interface to the I/O subsystem


An interrupt priority scheme can be used to ____.


Select one:
a. All the other answers
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,b.allow the most urgent work to be finished first
c.defer the handling of low-priority interrupt without masking off all interrupts
d.make it possible for high-priority interrupts to preempt the execution of a low priority
interrupt - ANS a. All the other answers


DMA controllers ____.


Select one:
a.are a nonstandard component in PCs of today
b.can steal memory access cycles from the main CPU
c.do not utilize an additional, special purpose, processor

d.can access main memory at the same time as the main CPU - ANS b.can steal memory
access cycles from the main CPU


The ____ register of an I/O port can be written by the host to start a command or to change the
mode of a device.


Select one:
a. status
b. transfer
c. data-in

d. control - ANS d. control


____ I/O accesses a block device as a simple array of blocks.


Select one:
a. Raw
b. Cooked
c. Stream

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,d. Indirect - ANS a. Raw


A character-stream device ____.


Select one:
a. is a device such as a disk drive
b.transfers data in blocks of bytes
c.transfers data a byte at a time

d. is similar to a random access device - ANS c.transfers data a byte at a time


Which of the following is true of a blocking system call?


Select one:
a.The application continues to execute its code when the call is issued.
b.Blocking application code is harder to understand than nonblocking application code
c.The call returns immediately without waiting for the I/O to complete.

d.The execution of the application is suspended when the call is issued. - ANS d.The execution
of the application is suspended when the call is issued.


Although caching and buffering are distinct functions, sometimes a region of memory can be
used for both purposes.


Select one:
True

False - ANS True


A sense key reports on the failure of a SCSI device by ____.


Select one:

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, a.giving detailed information about the exact cause of failure
b.stating the general category of failure
c.stating the general nature of the failure

d.maintaining internal pages of error-log information - ANS c.stating the general nature of
the failure


A(n) ____ is a buffer that holds output for a device that cannot accept interleaved data streams.


Select one:
a. cache
b. spool
c. escape

d. block device - ANS b. spool


On a read operation, the device driver first checks if the data already available in the buffer
cache.


Select one:
True

False - ANS False


In modern operating systems, dynamic loading and unloading allows


Select one:
a.adding new I/O devices without recompiling the kernel.
b.updating existing devices drivers without recompiling the kernel.
c.adding new I/O devices after the system has already been booted.

d. All the other choices - ANS d. All the other choices


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